Since the introduction of integrated circuits (ICs), engineers have been trying to increase the density of circuits on ICs, which reduces the cost of manufacturing of said ICs. One approach has been to put more components/functionality onto a chip. A second approach has been to build more chips on a larger wafer to reduce IC costs. For example, silicon wafer sizes have grown from averaging 3 inches in diameter in the 1960s to 12 inches today.
Various attempts were tried in the past to improve IC functionality, performance, and cost figures. Early IC implementations used bipolar junction transistors (BJTs), which have layers of various diffusion regions stacked vertically, and isolated transistor pockets containing the three switching terminals (base, emitter and collector), among other resistive (R) and capacitive (C) circuit elements. However, for the last decade of IC implementations, it was V-I signal and PHY parameter scaling that was used to house more components on a chip.
CMOS technology came after and surpassed BJT technology, which was relatively bulky, provided poor transistor yield, and exhibited high DC power usage. Device complexity has grown to over billions of circuit elements with Complementary MOS (CMOS) constructs. For more than 30 years a reduction in cost and increase in performance of CMOS technology has been achieved by shrinking the physical dimensions of CMOS transistors. These dimensions have shrunken to a size that is only a few molecular layers thick in critical device parameters. However, further shrinking of CMOS is running against limits imposed by the laws of physics. In addition to trying to manufacture tens of billions of these CMOS circuit elements with “molecular” dimensions, these dramatically smaller circuits operate with very low signal (voltage) levels, making their signal integrity susceptible to noise and causing speed degradation, and or power/heat run-off.